The first consideration for identifying the likely classification of the invention is recognition that a physical activity threshold of exercise/conditioning is not intended, and not likely achieved using the invention. Functionally, this Interactive Stance Mat provides relief from gravity typical to gel mats. It provides a dynamic interaction alternative to static sitting posture; an opportunity to structurally register the spine/posture using rhythmic motion; a cushion to gravity and more interactive with ground reaction forces than found in the comfort mat art. Invention field could be Stance Mat or Exercise Mechanism under class 482, or a new sub class. Inventor prefers to view the invention as a mat based on its structure and larger commercial market. Invention is directed to health and comfort, not conditioning. Physical properties of the mechanisms viscoelastic structure place it in a different category than known elastic devices; it is much less forceful in elastic response. It has the characteristic lag response common in viscoelasticity, reaction at a level generally only tactile to the user. Inventor is not sure of the applicable art.